In this work, we focus on other aspects of particle production due to gravitational effects. Specifically, gravity is believed to generate couplings between different sectors of the theory as long as these are
consistent with gauge symmetries. The corresponding operators may be non–renormalizable and thus suppressed by the Planck scale. Nevertheless, they can play an important role in dark matter production.
This was recently emphasised in [1]},[2]}, where the effects due to tree level graviton exchange were considered.
